Bill Seaver stands at his UpDesk most workday mornings, tapping away at his keyboard and manning the phones. The 37-year-old marketing consultant from Nashville, Tenn., bought the adjustable height desk for his home office about a year ago so he could move between sitting and standing whenever he felt like it.

"I bought it to help ease my back pain," he said. "I haven't messed up my back since I started using it."

Seaver said he loves his standing desk, which he believes has also helped him feel more fit. And if the thousands of glowing reviews on Amazon and UpDesk's website are any indication, many other Americans feel the same way.

Standing desks and their slow-moving cousins, treadmill desks, allow people to take a stand against prolonged sitting, which is so bad for your health, said experts. Some scientists have compared it to smoking. With so much movement engineered out of modern life, the idea is that rising up from your office chair and prying yourself from the couch for a few extra hours a day should lead to better health and lower the risk of heart disease, stroke and cancer.

Marc Hamilton, a professor of inactivity physiology at Pennington Biomedical Research Center in Baton Rouge, La., has led numerous studies that demonstrate the health dangers of sloth. He said there is little doubt that long periods of sitting carries health risks, but he has never seen evidence directly linking the use of standing or moving desks to improved health.

"It's a creative idea, but it's not been scientifically proven," he said. "As of now, there's really no research to show they do any good."

Hamilton doesn't believe there's any harm in using a standing desk but suspects it would supply borderline health benefits at best. He doubts whether it would cause the small muscles throughout the body to contract often enough to change the bad biochemistry that arises from too little movement.

"When you sit for long periods of time, there is very little contractile activity going on in the skeletal muscle, and after more than a thousand studies, we believe that small, low level contractions are very important for good health," he said.

Activities that initiate low level muscle contractions are the ones you do as you go about your everyday life without raising your heart rate or breaking a sweat, Hamilton explained. On their own, activities like standing in line, strolling to work and doing housework burn a minuscule number of calories, and just barely move the muscles, but over the course of the day, they add up.

After several hours without any such activity, studies find that the genes and enzymes regulating the amount of glucose and fat in the body diminish, resulting in fat from the bloodstream being captured and stored by fat cells all throughout the body.

The fat that wraps around the organs appears to be particularly damaging to your health. It's been linked to a wide range of major diseases, including heart disease, stroke, diabetes, cancer and osteoporosis.

Sitting for too long is not the same as exercising too little, Hamilton pointed out. A regular exercise program doesn't seem to cancel out the negative effects of minimal lifestyle movement. For example, a series of investigations done at the University of South Carolina found that men who were sedentary more than 23 hours a week had a 64 percent greater risk of dying from heart disease compared with those who reported less than 11 hours a week of sedentary activity, even if they exercised regularly.